Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$136.27	8.130%	$147.3488	$147.35	$147.35	$147.30
Purchase #2	$122.85	3.507%	$127.1583	$127.16	$127.15	$127.20
Purchase #3	$37.28	6.786%	$39.8098	$39.81	$39.80	$39.80
Purchase #4	$152.72	7.417%	$164.0472	$164.05	$164.05	$164.00
Purchase #5	$162.76	6.385%	$173.1522	$173.15	$173.15	$173.20
Purchase #6	$166.46	12.721%	$187.6354	$187.64	$187.65	$187.60
Purchase #7	$59.46	3.801%	$61.7201	$61.72	$61.70	$61.70
7 purchase totals =	$837.80		$900.8718	$900.88	$900.85	$900.80